12 Pounds extra Tire weight?
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
it's inertia that's the problem
BUT
moving to a better tire that's unavailable in the smaller sizes often will give you a better overall car
for example. in z06 world guys often move to the PSS on the heavier tsw wheels. performance is better even though you're adding about 4lbs a corner
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Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
2001 Z06---Took my hard rock goodyear tires off--replaced with OEM size Firestone Firehawk tires--from what I have gathered about tires weights--the firestones are about 2.5 to 3 lbs a tire more weight--I really cant feel a performance lost but I can feel traction gain for sure-So I added about 10-12 total pounds of unsprung weight- 
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Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
Yes my GY were hard as rocks--I bought the stones new in 2008/ date code confirms 0708-i was surprised that the GY were that much lighter--still had 7/32 tread-
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Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
if traction is a concern most people never run a tire over 3-4 years old
i do realize a lot of cruiser types go up to 10 years but the performance is REALLY down
Thread Starter
Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
Thread Starter
Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
Drifting
Joined: Mar 2011
Posts: 1,412
Likes: 15
From: Richardson TX
I would estimate that every pound of extra tire weight will AT MOST cost about 1 horsepower, and probably more like 1/2 of a horsepower.
So, 12lbs of tire weight, you're looking at a ballpark of 5-10 horsepower lost.
So, 12lbs of tire weight, you're looking at a ballpark of 5-10 horsepower lost.
Le Mans Master
Joined: Mar 1999
Posts: 6,029
Likes: 85
From: Palm Coast, FL
would this be close to a constant and still hold true as HP rises up the scale?
thanks ...
Pro
Joined: Aug 2012
Posts: 568
Likes: 1
From: Fresno California
Ain't it funny how one little three letter word can change everything.
You do have to be careful about how much weight you add with your tire and wheel combination. Shock absorber dynamics are cause for concern too.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Not sure if I buy 1 HP per pound lost due to wheel/tire inertial spin up power loss. If that was the case, then if four wheels+tires (40 lbs ea) = 160 lbs, you'd be losing 160 HP? So if the engine was rated at 400 HP at the crankshaft, you'd only be getting 240 HP to the ground to accelerate the car? Even if it was 1/2 HP per pound that would be 80 HP due to 160 lbs of wheels/tires mass ... still seems too high.
Last edited by ZeeOSix; Aug 11, 2013 at 03:42 PM.
Thread Starter
Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
Lets say im drag racing--traction with the firestones is ok--go to all 4 tires that are 10 lbs lighter--again traction is ok-I really don't think my timeslip would vary much at all--with everything else being equal-
Le Mans Master
Joined: Nov 2005
Posts: 5,403
Likes: 31
From: Allentown PA & Elk Twp NJ HPDE Addict
I've heard that 1 lb on the tires and wheels is equal to around 4 -6 lbs of sprung weight based on how far from the center of rotation the extra weight lies. That equates to roughly 50 to 60 more lbs..... or around 10 gallons of gas. I personally can't feel the performance difference between a full tank or quarter tabk of gas.